Mast supporting adjustability device

ABSTRACT

A drill rig having a universally mounted mast which is rigidly supported but moveable both transversely and rotationally in fore and aft and lateral directions. Novel mast support arrangements are disclosed including a free floating upper brace to accomodate relative vertical displacements of mast connection points which occur during rotational or tilting movements of the mast, and further including upper and lower crossbeams with connector elements separately moveable therealong and pivotally connected to the mast.

States Patent I MAST SUPPORTING ADJUSTABILITY DEVICE [75] Inventor:Eberhard V. Ranft, Houston, Tex.

[73] Assignee: Raymond International, Inc.,

Houston, Tex.

[22] Filed: May 1, 1974 [21] Appl. N0.: 466,076

[52] US. Cl. 52/116; 173/28; 173/43 [51] Int. Cl. E0411 12/34; 1521C9/00 [58] Field of Search 52/111, 116, 115; 173/43, 173/28; 212/8 R, 9;254/1391; 214/671, 75 H [56] References Cited UNITED STATES PATENTS808,132 12/1905 Williams 173/28 2,348,024 5/1944 Parrish 173/28 X2,598,454 5/1952 Smith 173/43 2,689,549 9/1954 Hayman 52/115 X 2,827,7723/1958 Taylor et a1. 173/28 X 2,904,310 9/1959 Leonard 173/43 X2,980,269 4/1961 Zimmerman 214/671 X 3,161,262 12/1964 Back 254/1391 X3,172,483 3/1965 Spitzer 173/28 X 3,225,842 12/1965 Roeschen 173/433,340,938 9/1967 Wilson 173/28 Primary Examiner-Henry C. SutherlandAssistant E\'aminerLeslie A. Braun Attorney, Agent, or Firm-Fitzpatrick,Cella, Harper & Scinto ABSTRACT A drill rig having a universally mountedmast which is rigidly supported but moveable both transversely androtationally in fore and aft and lateral directions. Novel mast support"arrangements are disclosed including a free floating upper brace toaccomodate relative vertical displacements of mast connection pointswhich occur during rotational or tilting movements of the mast, andfurther including upper and lower crossbeams with connector elementsseparately moveable therealong and pivotally connected to the mast.

15 Claims, 12 Drawing Figures Sheet 1 of8 US. Patent Nov. 18, 1975 US.Patent Nov. 18, 1975 Sheet 2 of8 3,919,816

US. Patent Nov. 18, 1975 Sheet3of8 3,919,16

Ticll.

US. Patent Nov. 18,1975 Sheet60f8 3,919,816

US. Patfiznt Nov. 18, 1975 Sheet 8 of8 3,919,816

MAST SUPPORTING ADJUSTABILITY DEVICE BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to moveable mast supportmechanisms and more particularlyit concerns novel structures foradjustably supporting a mastin different transverse and lateralpositions as well as-in different degrees of rotation or tilt withrespect to the base on which it is mounted. The present invention isparticularly suited to portable drill rigs and to other typesof derrickwhich are required toposition an elongated mast-like structure, such asa drill guide, accurately over predetermined locations, in the earth andto maintainthe structure firmly at a given degree of tilt while a drilling or other operation is carried out.

The present invention makes it possible for a drilling rig to supportits drilling mast rigidly at each o f-a range of transverse and fore andaft locations and to adjust the position of the mast with respect to thedrilling rig structure with high degree of accuracy. In addition thepresent invention also permits the drilling mast to be tilted or rotatedin both the fore and aft and lateral planes; and it also enables themast to be retracted from its operative upright position to a horizontalposition atop the rig so that the rig can ,be transported along highwaysand other routes requiring a limited overall vehicle height. I

2. Description of Known Prior Art U.$. Pat. Nos. 3,312,221 and 3,385,014show a pile drivingrig having a mast which is adjustably supported bymeans of bracing struts... The bracing struts are also arranged to allowthe mast to be moved to a horizontal position atop the rigfortransporting same. The bracing strut arrangements of this known priorart, however, do

not allow so universal a movementof the mast as is obtained with thepresent invention nor do they support the mast as rigidlywith sofewmoving parts as. is obtained with the present invention SUMMARY OF TI-IEINVENTIQN In one aspect, the present invention provides a mechanism foradjustably supporting a mast for fore and aft translational and tiltingor rotational movement with respect to a base such as a drill rigchassis. According to this aspect of the invention the lowerregion ofthe mast is pivotally supported in front of the base by a first mountingmeans near one edge of the base. A rear brace is connected at one end toextend up from a second location on the base behind the first location.An upper brace is freely pivotally connected between an upper point onthe mast and the other end of the rear brace; and an actuating mechanismis provided to cause the upper brace to move the upper region of themast back and forth. The upper brace is thus not required to supportanyof the mast weight and it merely needs to move the upper end of the mastfore and aft. Because the upper brace is freely pivoted with respect tothe rear brace it can readily' accomodate I any changes in the verticaldistance between the upper and lower mast connection points which occurwhen the mast is tilted. I a v I In the preferred embodiment the firstmounting means also comprises a spotter brace pivotally connectedbetween the front edge of the base and the lower point on the mast.Means are provided to control,

movements of the spotter bracein conjunction with those of. the upperbrace to produce for and aft translational and rotational mastmovements. Also in the preferred embodiment, the rear braceis pivotallyconnected to the base behind its front edge and actuating means arearranged to produce rotation of the rear brace so that the upper bracefore and aft movements can be controlled and so that the mast can beretracted to a horizontal position on top of the base fortransportation. This last mentioned means may take the form of hydraulicbatter piston and cylinder assemblies which extend from the base tolocations at or near the upper end of the rear brace. Where the base isa vehicle v Chassis it may be provided with wheels or tracks for mobilyt t Q I a According to a further aspect of the present invention thereare provided arrangements for obtaining lateral transverse androtational positioning of a mast. These arrangements include upper andlower cross beams with a mast connector element mounted for movementalong each beam. The connector elements are pivotally connected to upperand lower locations, respectively, on the mast and means are provided toaccomodate the different distances between the connectorelement-to-mast. connecting points, in the vertical direction as themast is rotated. In the preferred embodiment, the distance between theconnector element to mast connecting points is maintained fixed alongthelength of the mast and the different distances between these connectingpoints, which occur in the vertical direction when the mast is rotated,is accomodated by the provision of upper crossbeam mounting means whichsupports the beam rigidly in the fore and aft and lateral directions butallows free movement of the beam in the vertical direction.

There has thus been outlined rather broadly the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may'be better appreciated. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject of the claims appended hereto. Thoseskilled in the art will appreciate that the conception upon which thisdisclosure is based may readily be utilized as a basis for the designingof other structures and other methods for carrying out the severalpurposes of the invention. It is important, therefore, that the claimsbe regarded as including such equivalent structures and methods as donot depart from the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS A specific embodiment of the inventionhas been chosen for purposes of illustration and description, and isshown in the accompanying drawings forming a part of the specification,wherein:

FIG. 1 is a side elevational outline view .of a drill rig in which thepresent invention is embodied, and illustrating fore and aft mastpositioning configurations of the rig;

FIG. 2; is a front elevational outline view of the drill rig of FIG. 1,and illustrating lateral mast positioning configurations of the rig;

FIG. 3 is an enlarged sideelevational view of the drill rig of FIG. 1 inits mast retracting configuration;

FIG. 4 is a top plan view of the drill rig of FIG. 3;

FIG. Sis a further enlarged side elevational view, partially cut away,of the drill rig of FIG. I showing in detail various bracing assembliesfor mast positioning;

FIG. 6 is a front elevational view, partially cut away, of the drillrig, of FIG.

FIG. 7 is a view taken along line 7-7 of FIG. 5;

FIG. 8 is a top plan view of the drill rig of FIG. 5;

FIG. 9 is an enlarged view, partially cutaway of a cross-beam and mastmounting assembly taken along line 99 of FIG. 6;

FIG. 10 is a view taken along line l0l0 of FIG. 9;

FIG. 11 is an enlarged section view taken along line 11-11 of FIG. 10;and

FIG. 12 is a fragmentary perspective view, partially exploded showingselected portions of the cross-beam mounting assembly of FIGS. 9-11;

DESCRIPTION OF THE PREFERRED EMBODIMENT The drill rig shown in FIGS. 1-4comprises a main chassis assembly mounted on crawler tracks 22 formovement over a ground surface 24 with a maximum of traction and aminimum of unit ground pressure.

An elongated mast 26 of open framework construction is supported forcontrolled movements out in front of the main chassis assembly 20 by anovel system of braces. In general, this system of braces comprises aspotter brace assembly 28, a lower crossbeam assembly 30, a rear braceassembly 32, an upper brace assembly 34 and an upper crossbeam assembly36. The spotter brace assembly 28 extends forwardly from a spotter pivot38 on the front edge of the main chassis assembly 20 to a lowercrossbeam pivot 40 on the lower crossbeam assembly 30. The lowercrossbeam assembly 30, in turn is connected to a lower region of themast 26. A brace pivot assembly 42 interconnects one end each of therear and upper brace assemblies 32 and 34, while the opposite end of therear brace assembly is connected to a rear barce pivot 44 located on themain chassis assembly 20 rearwardly of the spotter pivot 38, and theopposite end of the upper brace assembly 34 is connected to an uppercrossbeam pivot 46 on the upper crossbeam assembly 36. The uppercrossbeam assembly in turn is connected to an upper region of the mast26. I

An hydraulic spotter piston and cylinder assembly 48 is pivotallyconnected between a spotter brace assembly pivot 49 near the lowercrossbeam pivot 40 and a spotter cylinder anchor point 50 located on themain chassis assembly 20 rearwardly of the spotter pivot 38. Also, anhydraulic batter piston and cylinder assembly 52 is pivotally connectedbetween the brace pivot assembly 42 and a batter cylinder anchor point54 located on the main chassis assembly 20 forwardly of the rear bracepivot 44.

It will be appreciated that by selective control of the extension andretraction of the spotter and batter piston and cylinder assemblies 48and 52, the spotter, rear and upper brace assemblies 28, 32 and 34 canbe articulated to move the mast 26 in a transverse rearward directionfrom its solid line position. indicated at A, to the phantom lineposition, indicated at B, or in both rotational and transversedirections to the phantom line positions indicated at C and D. Anyintermediate rotational and transational position can also be achievedby proper control of the relative actuation of the spotter and batterpiston and cylinder assemblies.

Turning now to FIG. 2, it will be seen that the mast 26 is also moveablcin a lateral direction, hoth transversely, as indicated by the phantomlines E and F, and rotationally. as indicated by the phantom line G andthe solid line position H. These movements are achieved by causingeither or both of the lower and upper crossbeam assemblies 30 and 36 tomove the mast laterally with respect to the lower and upper crossbeampivots 40 and 46 respectively. The particular construction of thecrossbeam assemblies 30 and 36 and the manner in which they produce thislateral mast movement will be described more fully hereinafter.

It should be noted that the distance along the length of the mast 26between the lower and upper crossbeam assemblies 30 and 36 is fixed.Further, since the crossbeam assemblies remain horizontal, the verticaldistance between them changes as the mast 26 is rotated or tiltedbetween either of its vertical positions E or F and either of itsrotated positions G or H. The mannner in which this verticaldisplacement is accomodated with the novel bracing system of the presentinvention can be seen in FIG. 1. It will be noted from FIG. 1 th af theupper brace assembly 34 is free to pivot via the brace pivot assembly 42as the batter piston and cylinder assembly 52 causes the rear brace 32to pivot about the rear brace pivot 44. The upper brace assembly 34 thusfloats with respect to the remainder of the system and provides lateralstability to the upper end of the mast 26. Because of the floatingcapability, the upper brace assembly 34 merely pivots downwardlyslightly to accomodate the varying vertical distances between the lowerand upper crossbeam assemblies 30 and 36 when they are actuated torotate the mast 26 laterally between its vertical and tilted positionsas shown in FIG. 2.

Turning now to FIGS. 3 and 4, it will be seen that the bracing systemcan be actuated to bring the mast 26 to a full horizontal position ontop of the main chassis assembly 20. With the mast in this position therig is quite compact and stabilized for travel either on its own crawlertracks 22 or on another vehicle.

In the enlarged views of FIGS. 3 and 4 it can be seen that the mainchassis assembly 20 is provided with an operators cab 56 positioned nearits front edge and offset laterally to permit retraction of the mast 26to its horizontal position. Toward the rear of the main chassis assemblythere is provided an engine compartment 58 wherein a crawler trackdriving engine is mounted. A main fuel tank 60 is located aft of theengine compartment 58. The region forwardly of the engine compartment istaken up with various power supply equipment for the drilling or otheroperations which the rig is to provide. Also hydraulic power and controlapparatus for actuation of the spotter and batter piston and cylinderassemblies and other hydarulic apparatus on the rig.

It will be noted from FIG. 3 that when the mast 26 is in its horizontalfully retracted position, the brace system is articulated such that itis essentially fully collapsed, with the batter piston and cylinderassembly 52 fully extended. While this does provide a very compactarrangement for transportation, it also reduces the mechanical advantageor leverage available to the batter piston and cylinder assembly 52 inthe initial stages of mast erection. In order to reduce the initialloading on the batter piston and cylinder assembly during the earlystages of mast erection, there is provided an hydraulic booster pistonand cylinder assembly 62. This assembly extends essentially verticallyfrom a booster anchor 64 on the main chassis assembly 20 to a pusher pad66 which rests against the side of the mast 26 in its horizontalposition. The manner in which this booster piston and cylinder assemblyoperates can best be seen in FIG. 5. During the initial stages of masterection, the booster piston and cylinder assembly are actuated andextended to urge the mast 26 upwardly so that it rotates about the lowercrossbeam pivot 40. When the mast reaches the position indicated by thephantom outline J in FIG. 5, the brace system is articulatedsufficiently to increase the mechanical advantage presented to thebatter piston and cylinder assembly 52 so that by actuating thisassembly in a retraction direction the brace system may continue to bearticulated to bring the mast to a full upright position.

There are several additional advantages which result from the bracingand actuation system described above; and these advantages can best beappreciated from a consideration of FIG. 5 of the drawings. Firstly, thespotter brace assembly 28, along withthe spotter pivot 38, and the lowercrossbeam pivot 40, cooperate to form a lower mounting arrangement bywhich the lower region of the mast 26 is pivotally mounted to the frontedge of the main chassis assembly 20. This lower mounting arrangement iscapable of supporting all of the mast weight, including the weight ofall equipment carried by the mast. The spotter brace assembly 28 extendssharply upwardly from the main chassis assembly 20 to the lowercrossbeam pivot 40 so that a minimal portion of the mast weight is borneby the spotter piston and cylinder assembly 48. Further, with thisarrangement, the spotter piston and cylinder assembly actuation isprimarily directed to fore and aft movement of the lower region of themast.

Because the mast weight is borne by the lower mounting arrangement, theaction of rear and upper brace assemblies 32 and 34 and the batterpiston and cylinder assembly 52 is used only to control fore and aftmovements of the upper regions of the mast 26. Thus, once the mast iserected to a generally upright attitude and is supported by the lowermounting assembly, positional adjustments of the upper portion of themast can be obtained by means causing fore and aft movement of the uppercrossbrace assembly 34. Where this means incorporates the rear and upperbrace assemblies 32 and 34 and the batter piston and cylinder assembly52, the stresses imposed on these elements is only minimal. Moreover,the placement of the batter piston and cylinder assembly is such thatwhen the mast is upright and is being positionally adjusted or spotted,the batter piston and cylinder assembly is in its more retractedcondition. Also the geometry of the bracing system in this condition issuch that relatively large piston and cylinder movements are needed toproduce rather small amounts of mast movement. This allows forsignificantly fine control and accurate positioning or spotting of themast.

When the mast is retracted to its horizontal position as shown inphantom outline in FIG. 5 the batter piston and cylinder assembly 52 isfully extended. This is due to the positioning of the batter cylinderanchor points 54 forwardly of the rear brace pivot 44. As a result, thebatter piston and cylinder assembly is subjected only to tensile forcesduring mast retraction and erection movements. This permits a lighterweight construction than would be needed in the case where highcompressive forces are encountered.

As shown in FIG. 5 a drill guide 68 and associated drilling equipment 70are mounted on the mast 26 for drilling operations where the mast iserected. This I equipment may remain on the mast where it is retractedso that minimal dissassembly is needed for transporting the drill rig.

As can be seen in FIGS. Sand 6 the mast 26 is of scribed in detailhereinafter, may be actuated to move the mast 26 laterally as indicatedby the arrows L and M. When both crossbeam assemblies produce the sameamount of movement in the same direction the mast undergoes lateraltranslational movement; but when the crossbeam assemblies are actuatedto produce different amounts of movement or movements is differentdirections the mast is then rotated or tilted accordingly.

It will also be seen from FIG. 6 that the spotter brace assembly 28comprises a pair of spotter braces 28a and 28b each connected to themain chassis assembly 20 and to the lower crossbeam assembly 30 by meansof individual ones of the spotter pivots 38 and the lower crossbeampivots 40.

As shown in FIG. 7 the rear brace assembly 32 is built up of tubularsteel in the form of a flat framework. The upper and lower ends of therear brace assembly are each provided'with spaced apart knuckles 72which form portions of the brace pivot assembly 42 and the rear bracepivot 44. The batter piston and cylinder assembly 52 also comprises apair of batter piston and cylinders 52a and 52b each connected to spacedapart locations on the brace pivot assembly 42 and each extending downto associated batter cylinder anchor points 54.

As shown in FIG. 8, the upper brace assembly 34 is of similarconstruction to that of the rear brace assembly 42; and it also isprovided with spaced apart knuckles 63 which form portions of the bracepivot assembly 42 and the upper crossbeam pivot 46. The framelikeconstruction of the mast 26 and the rear and upper brace assemblies 32and 34 and their spaced apart pivotal interconnections results in anoverall box-like configuration made up of the mast 26 the upper braceassembly 34 the rear brace assembly 32, and the main chassis assembly20. This provides a high degree of rigidity for a relatively lightweight structure. The upper and lower crossbeam assemblies 30 and 36 areof the same construction; and accordingly only the upper crossbeamassembly 36 will be described herein. The construction of this assemblyis best shown in FIGS. 6 and 9-12.

As shown in FIG. 9 the knuckles 74 of the upper brace assembly 34 arepinned to connecting lugs 76 to form the upper crossbeam pivot 46. Thelugs ".76 in turn are welded to an elongated rail-like leader 78 whichextends horizontally of the rig. The leader 78, as shown in FIG. 12 hasupper and lower rails 80 and a central lengthwise channel 82. Further,as shown in FIGS. 9 and 11, a double rod end cylinder and pistonassembly 84 is bolted to the leader 78 half way along its length andinside the channel 82. This lateral piston and cylinder assembly 84 ismounted to extend along the channel 82 with its rod ends in mutuallyopposite directions and fastened by pin connection 86 to puller plates88.

The lateral piston and cylinder assembly extends out beyond the ends ofthe leader 78 where it is connected to the puller plates 88. Thesepuller plates are interconnected by upper and lower flanged braces 90which extend along parallel to and just above and below the leader 78. Aleader carriage 92 is mounted between the flanged braces 90 midway alongtheir length. This leader carriage comprises a front plate 94, and upperand lower rear plates 96 welded together in spaced apart relationship bymeans of gussets 115. This welded carriage assembly, consisting ofplates 94, 96 houses a group of upper and lower rollers 98 which ride onthe rails 80 of the leader 78 and which have axles 100 extending throughthe front plate 94 and the rear plates 96. Locking nuts 102 are threadedto the axles 100 outside the plates. Cover plates 104 are fastened inplace between the plates to protect the rollers 98 from infiltration offoreign matter. Further, as shown in FIG. 11, bronze wear pads 106 areprovided between the plates and the sides of the rails 80 to providesmooth low friction carriage movement.

It will be seen from the foregoing that the leader 78 is secured by thelugs 76 to the upper crossbeam pivot 46 and that the carriage 92 ismoveable back and forth with the rollers 98 riding on the rails 80 ofthe leader. Actuation of this carriage movement is produced by thelateral piston and cylinder assembly whose piston rod movements arecommunicated to the puller plate 88, whose movements in turn arecommunicated through the braces 90 to the carriage 92.

A mast connecting pin 108 extends forwardly from the front plate 94; andas shown in FIG. 9 this pin is pivotally corrected to the mast 26. Themast is provided with a cross plate 110 having an opening 112 throughwhich the pin 108 extends. A lock ring 114 secures the pin in place inthe plate 110 while allowing rotational movement between the two.

In operation of the crossbeam assemblies 30 and 36 their associatedcarriages 92 are moved laterally back and forth along the leaders 78.When the carriage movements are together in the same direction, the mastis moved transversely in that direction. However, when the carriages aremoved in different amounts or in opposite directions, the mast 26 isrotated or tilted laterally.

It will be noted that when the mast is thus rotated the verticaldistance between the upper and lower crossbeam carriage 92 changesalthough the actual distances between the carriages, along the length ofthe mast remains the same. This vertical displacement is accomodated bythe bracing system which supports the upper crossbeam assembly 36 insuch a way that it is held rigidly against lateral and against fore andaft movement while being free to undergo vertical movement. This freevertical movement is achieved by the brace pivot assembly which allowsfree up and down pivoting of the upper brace assembly 34. It will thusbe seen that in the present embodiment the same brace system with freefloating upper brace accomodates not only fore and aft rotationalmovements of the mast but also lateral rotational movements of the mast.

Although a particular embodiment of 'the invention is herein disclosedfor purposes of explanation, various modifications thereof, after studyof this specification,

will be apparent to those skilled in the art to which the inventionpertains.

What is claimed and desired to be secured by letters patent is:

. 1. A mechanism for adjustably supporting a mast from a base member,said mechanism comprising a first mounting means pivotallyinterconnecting a lower point on said mast in front of a first locationof said base member near one edge thereof, a rear brace connected at oneend to extend up from a second location on said base member behind saidfirst location, an upper brace freely pivotally connected between. anupper point on said mast and the other end of said rear brace andextendable actuating means for causing forward and rearward movement ofsaid upper brace and pivotal movement of said rear brace with respect tosaid base, said actuating means being pivotally fastened to said basemember between said first and second locations and connected to at leastone of said upper and rear braces, the length of said upper and rearbraces and the extensibility of said actuating means being sufficient topermit the mast to be retracted to a horizontal transport position ontop of said base.

2. A mechanism according to claim 1 wherein said first mounting meanscomprises a brace extending between and pivotally connected to saidlower point on said mast and said first location on said base and afurther actuating means for controlling pivotal movements of said firstbrace with respect to said base member.

3. A mechanism according to claim 2 wherein said further actuating meanscomprises an hydraulic piston and cylinder assembly extending between apivot on said base above said first location and a pivot near said lowerpoint on said mast.

4. A mechanism according to claim 1 wherein said actuating meanscomprises hydraulic piston and cylinder means.

5. A mechanism according to claim 1 wherein said mast is moveablelaterally with respect to said first mounting means and said upperbrace.

6. A mechanism according to claim 5 wherein crossbeams are connectedrespectively to said first mounting means and to said upper brace, eachcrossbeam having a carriage moveable therealong and means pivotallyconnecting said carriages to said lower and upper points on said mastrespectively.

7. A mechanism according to claim 1, wherein said actuating means isconnected to a brace pivot assembly which interconnects the upper andrear braces.

8. A mechanism for adjustably supporting a mast from a base member, saidmechanism comprising upper and lower generally horizontal crossbeams, abracing mechanism on said base member and supporting said crossbeams toextend in parallel relationship one above the other, a connector elementmounted for movement along the length of each crossbeam, means forseparately controlling the movements of said connector elements andpivot means interconnecting said connector elements respectively, toupper and lower locations on said mast for relative pivotal movementsabout generally horizontal axes perpendicular to said crossbeams, atleast one of said pivot means being freely moveable in a verticaldirection with respect to said bracing mechanism.

9. A mechanism according to claim 8 wherein actuator means areinterconnected between said crossbeams and their respective connectorelements;

10. A mechanism according to claim 9 wherein said actuator meanscomprises hydraulic piston and cylincler means secured to and extendinglengthwise of said crossbeams.

11. A mechanism according to claim 10 wherein each connector element isprovided with a brace extending therefrom parallel to and beyond the endof the associated crossbeam and means at the end of said braceinterconnecting said brace to a moveable portion of the associatedhydraulic piston and cylinder means.

12 A mechanism according to claim 8 wherein said bracing mechanism isconstructed to maintain said crossbeams rigidly positioned againstmovement in the fore and aft and lateral directions and the lowercrossbeam against movement in the vertical direction while permittingfree vertical movement of the upper crossbeam.

13. A mechanism according to claim 8 wherein said pivot means are eachfixedly located on said mast.

14. A mechanism according to claim 8 wherein said bracing mechanismincludes a generally horizontally extending upper brace pivotallyconnected at one end to said upper crossbeam and freely pivotallyconnected at its opposite end to another portion of the bracingmechanism.

15. A mechanism according to claim 8 wherein said crossbeams are formedwith rails along their length and wherein said connector elements haverollers fitted to roll along each rail.

1. A mechanism for adjustably supporting a mast from a base member, saidmechanism comprising a first mounting means pivotally interconnecting alower point on said mast in front of a first location of said basemember near one edge thereof, a rear brace connected at one end toextend up from a second location on said base member behind said firstlocation, an upper brace freely pivotally connected between an upperpoint on said mast and the other end of said rear brace and extendableactuating means for causing forward and rearward movement of said upperbrace and pivotal movement of said rear brace with respect to said base,said actuating means being pivotally fastened to said base memberbetween said first and second locations and connected to at least one ofsaid upper and rear braces, the length of said upper and rear braces andthe extensibility of said actuating means being sufficient to permit themast to be retracted to a horizontal transport position on top of saidbase.
 2. A mechanism according to claim 1 wherein said first mountingmeans comprises a brace extending between and pivotally connected tosaid lower point on said mast and said first location on said base and afurther actuating means for controlling pivotal movements of said firstbrace with respect to said base member.
 3. A mechanism according toclaim 2 wherein said further actuating means comprises an hydraulicpiston and cylinder assembly extending between a pivot on said baseabove said first location and a pivot near said lower point on saidmast.
 4. A mechanism according to claim 1 wherein said actuating meanscomprises hydraulic piston and cylinder means.
 5. A mechanism accordingto claim 1 wherein said mast is moveable laterally with respect to saidfirst mounting means and said upper brace.
 6. A mechanism according toclaim 5 wherein crossbeams are connected respectively to said firstmounting means and to said upper brace, each crossbeam having a carriagemoveable therealong and means pivotally connecting said carriages tosaid lower and upper points on said mast respectively.
 7. A mechanismaccording to claim 1, wherein said actuating means is connected to abrace pivot assembly which interconnects the upper and rear braces.
 8. Amechanism for adjustably supporting a mast from a Base member, saidmechanism comprising upper and lower generally horizontal crossbeams, abracing mechanism on said base member and supporting said crossbeams toextend in parallel relationship one above the other, a connector elementmounted for movement along the length of each crossbeam, means forseparately controlling the movements of said connector elements andpivot means interconnecting said connector elements respectively, toupper and lower locations on said mast for relative pivotal movementsabout generally horizontal axes perpendicular to said crossbeams, atleast one of said pivot means being freely moveable in a verticaldirection with respect to said bracing mechanism.
 9. A mechanismaccording to claim 8 wherein actuator means are interconnected betweensaid crossbeams and their respective connector elements.
 10. A mechanismaccording to claim 9 wherein said actuator means comprises hydraulicpiston and cylinder means secured to and extending lengthwise of saidcrossbeams.
 11. A mechanism according to claim 10 wherein each connectorelement is provided with a brace extending therefrom parallel to andbeyond the end of the associated crossbeam and means at the end of saidbrace interconnecting said brace to a moveable portion of the associatedhydraulic piston and cylinder means.
 12. A mechanism according to claim8 wherein said bracing mechanism is constructed to maintain saidcrossbeams rigidly positioned against movement in the fore and aft andlateral directions and the lower crossbeam against movement in thevertical direction while permitting free vertical movement of the uppercrossbeam.
 13. A mechanism according to claim 8 wherein said pivot meansare each fixedly located on said mast.
 14. A mechanism according toclaim 8 wherein said bracing mechanism includes a generally horizontallyextending upper brace pivotally connected at one end to said uppercrossbeam and freely pivotally connected at its opposite end to anotherportion of the bracing mechanism.
 15. A mechanism according to claim 8wherein said crossbeams are formed with rails along their length andwherein said connector elements have rollers fitted to roll along eachrail.